Silver stain can detect as low as 1 ng.

Coomassie Blue R-250 can detect as low as 100 ng.

Coomassie Blue G-250 can detect as low as 10 ng.

Ok thanks reason i asked is that ive found of late that with a particular batch of Coomasie R 250 it seems to be detecting low amts of protein better than even silver anyway today i am running a gel and planning to stain with both  -

Although proteins can be detected by silver stain and coomassie blue at very low concentrations (values cited by Syed A Ali), the main protocols suggest to use higher protein concentration to be sure that you are detecting 100% of the proteins you have in your sample.

From my experience working with comassie blue R-250 what I can say is that bands profile are quite different for the same sample when using 5 ug instead of 25 ug.